Ive been practicing screaming for a couple of weeks and it sounds pretty good! when i do my high screams it sounds really good. when i do my medium screams its okay and i still sorta got to work on my low screams. but there is a problem I'm having. After a while of screaming for about 30 minutes i tend to start gaging. Then when i try to scream it gets harder for me because of that. Am i really screaming properly? What are the possibilities i might be doing wrong? please some one answer!